Bucket for elastic-fluid turbines.



s. A. MOSS. BUCKET FOR ELASTIC FLUID TURBINES. APPLICATION FILED JULY 20, 1907.

Patented Jan. 19, 1909.

Witnesses Inventor,

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"less will be the eddies introduced.

UNITED STATES PATEN 1 OFFICE.

SANFORDA. Moss, on LYNN, MASSACHUSETTS, ASSIGNOR TO GENERAL ELscTRic COMPANYV .Acoeromrror or new roan.

BUCKET FOR ELASTIC-FL'E TID TURBINES.

Specification of Letters Patent.

Patented J'an. '19; 1909.

Application filed m 20, 1907. Serial No. 384,780.

citizen of the United States, residing at Lynn, county of Essex, State of Massachusetts, have invented certain new and useful Improvements in Buckets for Elastic-Fluid Turbines, of which the following is a specification.

This invention relates to turbines actuated by elastic fluid, such as steam, and its object isto give such shapes to the buckets, both moving and stationary, that the shock angle willbe kept at or near a constant value for the entire series.

' In turbines which comprise a series of wheel buckets and intermediates, it is usual, for reasons which need not be here explained, to have the entrance angles of successive buckets increase from row to row. In many turbines the angles vary as follows: 24, 26, 2, 38, 45. Now the shock angle varies directly with the entrance angle and with the ratio of pitch to Width of bucket. The shock angle is that between the line of the entering stream of steam and a tangent to the curve of the bucket at the point wheresaid stream impinges upon it. Owing to the width of the stream, the various portions of it cannot be all turned at the,

same point, and the shock angle gives a measure 'of the losses due to the bending of the enterin therein. 'fiie smaller the shock angle isI, the

t is therefore possible to lessen these eddy losses by modifying the pitch and width of each successive bucket so that although the entrance angles increase successively yet the shock angles shall remain constant or nearly so.

It has been found that the cosineof the shock angle can be expressed mathematically'as 1 W sin. 2a, where is the pitch, W

the Width and a the entrance angle of the bucket. If, therefore, it is desired to keep the shock angle constant, in a series where the entrance angle increases, it can be done by choosing for each bucket a pitch and a width which will give a constant value to the above expression. 1

It is not necessary that the shock angle be mathematically the same for each row of buckets, but only that care be taken to prevent it from becoming 'injuriously large. The principle to be kept in mind is that in a successively decrease.

-constant. -mode, and Fig. 3 illustrates the third mode.

series of wheel and intermediate buckets in which the entrance angle successively increases, the ratio of pitch to width must This may be effected by increasing the width and keeping the pitch constant, or by keeping the width constantand decreasing the pitch, or by varying both the width and pitch irregularly in such a way thattheir ratio decreases.

In the accompanying drawing, Figure 1 is a diagram illustrating the first of the abovementioned modes of keeping the shock angle Fig. 2 illustrates the. second Referring first to Fig. 1, the entrance angles a of the alternate buckets and intermediates 1, 2, 3, 4, 5 are respectively 24, 26, 32, 38 and 45. The shock angle l/J for each bucket and intermediate is 39.

this case, the pitch is assumed to be constant at say .30 inches, and the widths of the buckets and intermediates var approxi mately as follows: bucket 11, 1 inc ;-intermediate 2, 1.071; bucket 3, 1.225; intermediate 4, 1.304; bucket 5, 1.333.

In Fig. 2, the entrance angles and the shock angle are the same as in I ig. 1, and the width is assumed to be constant at say one inch. In this case, the requirements of the formula give the successive pitches approxi- 5 v [mately as follows: 0.30, 0.28, 0.245, 0.23, stream and the resulting eddies In Fig. 3, we have'still the same entrance and shock angles as in the two preceding)fig;

ures, but the width and the pitch are varied for each bucket and intermediate, in such manner as still to maintain a constant value for the shock angle in the formula,

cos. 1 W sin. 20.. The successive ratios given to P and W in Fig. 3 are approximately as follows:

larly.

In accordance withthe provisions of the patent statutes, I have described the prmciple of operation of my invention together with the a paratus which I now consider to re resent 518 best embodiment thereof; but I e'sire to have it understood that the apparatus shown is only illustrative, and that the invention can be carried out by other means. What I claim as new and desire to secure by Letters Patentof the United States, is,

1. A series of turbine buckets, having successively changing entrance angles, and in which the ratio of itch to width changes inversely to said ang es.

2. A' series of turbine buckets, having successivel changing entrance an les a, and in which t 'e shock an le 1! for (me 1 bucket has a value determined ,by the expression cos.

=-1 P sin. in which ex ression P desi W P g na tes the pitch of the buckets, W represents the width of said buckets, and the quantity" lsin. 20 has an assigned value which which the ratio of pitch to width successively decreases.-

cessively increasing entrance angles a, and in Y which the shock angle 1/: has a constant value which is determined by the formula cos.

= 1 E sin. 2a inwhich P represents the pitch of the buckets, W represents the width of said buckets and the expression 1 W sin.

2a has a constant .value which isobtained by varying the ratio between P and W.

6. A series of turbine buckets having successivel increasing entrance angles, and in which the shock angle is kept substantially constant by varying the ratio between the pitch and the width of the buckets.

' In'witness Whereof,.I have hereunto set my hand this eighteenth day of July, 1907.

g SANFORD A. MOSS Witnesses:

JOHN A. MoMANUs, Jr., ALVARADO LA ROY ELL/IS 

